In semiconductor manufacturing, the washing processes are key processes in carrying out oxidation and diffusion, epitaxial growth, silicide formation, thin film formation, ion implantation, dry etching, and pre- or post-processing such as various types of heat treatment and the like. The proportion of the total process steps occupied by the washing processes is approximately 30%, and the area of the clean room occupied by the supply facilities, preparation facilities, and transportation facilities of the large amount of ultra-pure water or cleaning liquid, and by the washing facilities, is very large. Furthermore, the number of washing processes has increased with increasing integration of the semiconductor devices.
On the other hand, the degree of cleanliness of the wafers has approached a completely clean state, and the size of the wafers has further increased to a level of 12 inches, so that it will be increasingly difficult to guarantee uniformity and completeness of the washing.
Liquid crystal display (LCD) substrate washing processes are essentially identical to semiconductor substrate washing processes and are also in need of a thorough revolution. In the following explanation, the case of semiconductor wafers will chiefly be discussed as a representative of both semiconductor wafers and LCDs.
In the course of studying washing processes, the present inventors learned that in the "job shop method" employed in conventional semiconductor substrate washing processes, that is to say, in the method in which the wafers are transported to a washing area in each process step and after washing are transported to the treatment apparatus of the following step, the wafer movement distance is extremely large, and during wafer movement, the washing surfaces become recontaminated, and this constitutes a hindrance to development of more highly functional devices. In order to solve such recontamination problems, it is necessary to change the washing method from the conventional "job shop method" to a closed manufacturing continuous treatment method in which a washing apparatus is coupled to each process treatment apparatus and the pretreatment is conducted for that process. In order to accomplish this, it is desirable that a number of washing apparatuses equal to the number of washing processes be installed, and a reduction in size of the washing apparatuses is important.
Furthermore, the conventional washing process is conducted by means of a "batch method" in which wafers are immersed in a washing tank in units of ten, or in other words, by a "wafer parallel washing format". In order to increase throughput, it is necessary to reduce the gap between the parallel wafers, and as a result, it is fundamentally difficult to ensure uniformity of the insertion and discharge time of the washing solution per wafer, and the cleaning liquid flow. Furthermore, there is a drawback in that the front surface of the wafer is constantly affected by contamination from the rear surface of the wafer. Furthermore, there is also a problem in that time is required for the orderly movement of wafers to washing tanks having different cleaning liquids, and a large amount of time is required for the introduction of cleaning liquid into and discharge of cleaning liquid from the washing tanks.
Furthermore, in the conventional washing processes, there is a problem in that the amount of cleaning liquid or ultrapure water employed was very large.
The present invention has as an object thereof to solve the problems described above which were present in the conventional washing method. In other words, the present invention has as an object thereof to provide a washing apparatus which is capable of further improving the washing effect and enables highly clean washing using a small amount of chemicals.
Furthermore, it is an object to provide a washing apparatus of high throughput involving rapid switching of various chemicals of high responsiveness and capable of performing a series of washing operations at high speed.
Furthermore, it is an object to reduce the size of the washing apparatus itself.
Furthermore, the present invention has as an object thereof to provide a washing method which is capable of further improving the washing effect and which enables highly clean washing using a small amount of chemicals.